In the manufacture of an electronic device, an opening is formed in an insulating film on a silicon region and a contact connected to the silicon region is formed in the opening. The contact is made of, for example, titanium. Before the contact is formed, a silicon oxide film (natural oxide film) constituting a surface of the silicon region is removed. This silicon oxide film is exposed at a bottom of the opening.
Isotropic etching is generally used to remove the silicon oxide film before the contact is formed. An example of the isotropic etching may include chemical etching in which fluorine and a basic gas in a process gas react with silicon oxide of a silicon oxide film to form an altered region from the silicon oxide film. The altered region formed is removed by heating.
In the isotropic etching as described above, an insulating film is also etched along the lateral direction from a surface defining the opening. When the insulating film is etched, current leakage may occur between contacts of the fabricated electronic device. Therefore, it has been required to etch the silicon oxide film exposed at the bottom of the opening formed in the insulating film while suppressing the insulating film from being etched.